keywords) used inprotocols in the Internet community. Distribution of this memo is unlimited.

OVERVIEW

THIS RFC IS A SNAPSHOT OF THEONGOING PROCESS OF THE ASSIGNMENTOF PROTOCOL PARAMETERS FOR THEINTERNET PROTOCOL SUITE. TO MAKETHE CURRENT INFORMATION READILYAVAILABLE THE ASSIGNMENTS AREKEPT UP-TO-DATE IN A SET OF ONLINETEXT FILES. THIS RFC HAS BEENASSEMBLED BY CATINATING THESEFILES TOGETHER WITHA MINIMUM OFFORMATTING "GLUE". THE AUTHORSAPPOLOGIZE FOR THE SOMEWHATROUGHER FORMATTING AND STYLETHAN IS TYPICAL OF MOST RFCS.

We expect that various readers will notice specific items that should be corrected. Pleasesend any specific corrections via email to <iana@isi.edu>.

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INTRODUCTION

The files in this directory document the currently assigned values for several series ofnumbers used in network protocol implementations.

ftp://ftp.isi.edu/in-notes/iana/assignments

The Internet Assigned Numbers Authority (IANA) is the central coordinatorfor the assignment of unique parameter values for Internet protocols. TheIANA is chartered by the Internet Society (ISOC) and the Federal NetworkCouncil (FNC) to act as the clearinghouse to assign and coordinate the use ofnumerous Internet protocol parameters.

The common use of the Internet protocols by the Internet community requires that theparticular values used in these parameter fields be assigned uniquely. It is the task of theIANA to make those unique assignments as requested and to maintain a registry of thecurrently assigned values.

REQUESTS FOR PARAMETERASSIGNMENTS (PROTOCOLS, PORTS, ETC.)SHOULD BE SENT TO <IANA@ISI.EDU>.

REQUESTS FOR SNMP NETWORKMANAGEMENT ASSIGNMENTS SHOULDBE SENT TO <IANA-MIB@ISI.EDU>.

The IANA is located at and operated by the Information Science Institute (ISI) of theUniversity of Southern California (USC).

If you

are developing a protocol or application that will require the use of a link, socket, port,protocol, etc., please contact the IANA to receive a number assignment.

Joyce K. Reynolds

Internet Assigned Numbers Authority

USC-

Information Sciences Institute

Marina del Rey, California 90292-6695

Electronic mail: IANA@ISI.EDU

Phone: +1 310-822-1511

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MOST OF THE PROTOCOLS AREDOCUMENTED IN THE RFC SERIES OFNOTES. SOME OF THEITEMS LISTED AREUNDOCUMENTED. INFORMATION ONPROTOCOLS CAN BE FOUND IN THEMEMO, "INTERNET OFFICIAL PROTOCOL

STANDARDS" (STD 1).

Data Notations

The convention in the documentation of Internet Protocols is to expressnumbers in decimal and to picture data in "big-endian" order [COHEN].That is, fields are described left to right, with the most significant octet on theleft and the least significant octet on the right.

The order of transmission of the header and data described in this document is resolved to theoctet level. Whenever a diagram shows a group of octets, the order of transmission of thoseoctets is the normal order in which they are read in English. For example, in the followingdiagram the octets are transmitted in the order they are numbered.

0 1 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| 1 | 2 | 3

| 4 |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| 5 | 6 | 7 | 8 |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

| 9 |10 | 11 | 12 |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Transmission Order of Bytes

Whenever an octet represents a numeric quantity the left most bit in the diagram is the high

order or most significant bit. That is, the bit labeled 0 is the most significant bit. Forexample, the following diagram represents the value 170 (decimal).

0 1 2 3 4 5 6 7

+-+-+-+-+-+-+-+-+

|1 0 1 0 1 0 1 0|

+-+-+-+-+-+-+-+-+

Similarly, whenever a multi-octet field represents a numeric quantity the left most bit of thewhole field is the most significant bit. When

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a multi-octet quantity is transmitted the most significantoctet is

transmitted first.

Special Addresses

There are five classes of IP addresses: Class A through Class E. Of these, Classes A, B, andC are used for unicast addresses, Class D is used for multicast addresses, and Class Eaddresses are reserved forfuture use.

WITH THE ADVENT OF CLASSLESSADDRESSING [CIDR1, CIDR2], THENETWORK-NUMBER PART OF ANADDRESS MAY BE OF ANY LENGTH, ANDTHE WHOLE NOTION OFADDRESSCLASSES BECOMES LESS

IMPORTANT.

There are certain special cases for IP addresses. These special CASE can beconcisely summarized using the earlier notation for an IP address:

IP-address ::= { <Network-number>, <Host-number> }

or

IP-address ::= { <Network-number>, <Subnet-number>,

<Host-number> }

if we also use the notation "-1" tomean the field contains all 1

bits. Some common specialcases are as follows:

(a)

{0, 0}

This host on this network. Can only be used as a source

address (see note later).

(b)

{0, <Host-number>}

Specified host on this network. Can only be used as a

source address.

(c)

{-1,-1}

Limited broadcast. Can only be used as a destination

address, and a datagram withthis address must never be forwarded outside the (sub-)net of the source.

(d)

{<Network-number>,-1}

Directed broadcast to specified network. Can only be used as a destination address.

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(e)

{<Network-number>, <Subnet-number>,-1}

Directedbroadcast to specified subnet.Can only be used as a destinationaddress.